By ear. Yes, Musick.

Not to write about scales per se, but:

And beauty is in the ear of the beholding culture. We've written about this before on this board, but it bears repeating:

Different western cultural orchestras tune their concert A's differently--American orchestras tune to a different A from European orchestras. And the baroque orchestras tuned to the lowest A I'm aware of.

So, there are ears and there are other ears.

I don't mind at all since I don't have perfect pitch.